Advances in sperm analysis: techniques, discoveries and applications

Microfluidic sperm sorting selects a subpopulation of high-quality sperm with a higher potential for fertilization

STUDY QUESTION

Is a microfluidic sperm sorter (MSS) able to select higher quality sperm compared to conventional methods?

SUMMARY ANSWER

The MSS selects sperm with improved parameters, lower DNA fragmentation, and higher fertilizing potential.

WHAT IS KNOWN ALREADY

To date, the few studies that have compared microfluidics sperm selection with conventional methods have used heterogeneous study population and have lacked molecular investigations.

STUDY DESIGN, SIZE, DURATION

The efficiency of a newly designed MSS in isolating high-quality sperm was compared to the density-gradient centrifugation (DGC) and swim-up (SU) methods, using 100 semen samples in two groups, during 2023-2024.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Semen specimens from 50 normozoospermic and 50 non-normozoospermic men were sorted using MSS, DGC, and SU methods to compare parameters related to the quality and fertilizing potential of sperm. The fertilizing potential of sperm was determined by measurement of phospholipase C zeta (PLCζ) and post-acrosomal sheath WW domain-binding protein (PAWP) expression using flow cytometry, and the chromatin dispersion test was used to assess sperm DNA damage.

MAIN RESULTS AND THE ROLE OF CHANCE

In both normozoospermic and non-normozoospermic groups, the MSS-selected sperm with the highest progressive motility, PLCζ positive expression and PLCζ and PAWP fluorescence intensity the lowest non-progressive motility, and minimal DNA fragmentation, compared to sperm selected by DGC and SU methods (P < 0.05).

LIMITATION, REASONS FOR CAUTION

The major limitations of our study were the low yield of sperm in the MSS chips and intentional exclusion of severe male factor infertility to yield a sufficient sperm count for molecular experiments; thus testing with severe oligozoospermic semen and samples with low count and motility is still required. In addition, due to ethical considerations, at present, it was impossible to use the sperm achieved from MSS in the clinic to assess the fertilization rate and further outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

Our research presents new evidence that microfluidic sperm sorting may result in the selection of high-quality sperm from raw semen. This novel technology might be a key to improving clinical outcomes of assisted reproduction in infertile patients.

STUDY FUNDING/COMPETING INTEREST(S)

The study is funded by the Iran University of Medical Sciences and no competing interest exists.

TRIAL REGISTRATION NUMBER

N/A.

Automatic high-throughput and non-invasive selection of sperm at the biochemical level

BACKGROUND

Sperm selection, a key step in assisted reproductive technology (ART), has long been restrained at the preliminary physical level (morphology or motility); however, subsequent fertilization and embryogenesis are complicated biochemical processes. Such an enormous "gap" poses tough problems for couples dealing with infertility, especially patients with severe/total asthenozoospermia .

METHODS

We developed a biochemical-level, automatic-screening/separation, smart droplet-TO-hydrogel chip (BLASTO-chip) for sperm selection. The droplet can sense the pH change caused by sperm's respiration products and then transforms into a hydrogel to be selected out.

FINDINGS

The BLASTO-chip system can select biochemically active sperm with an accuracy of over 90%, and its selection efficiency can be flexibly tuned by nearly 10-fold. All the substances in the system were proven to be biosafe via evaluating mice fertilization and offspring health. Live sperm down to 1% could be enriched by over 76-fold to 76%. For clinical application to patients with severe/total asthenozoospermia, the BLASTO-chip could select live sperm from human semen samples containing 10% live but 100% immotile sperm. The rates of fertilization, cleavage, early embryos, and blastocysts were drastically elevated from 15% to 70.83%, 10% to 62.5%, 5% to 37.5%, and 0% to 16.67%, respectively.

CONCLUSIONS

The BLASTO-chip represents a real biochemical-level technology for sperm selection that is completely independent of sperm's motility. It can be a powerful tool in ART, especially for patients with severe/total asthenozoospermia.

FUNDING

This work was funded by the Ministry of Science and Technology of China, the Ministry of Education of China, and the Shenzhen-Hong Kong Hetao Cooperation Zone.

Effect of Aqueous Extract of Unripe Musa Paradisiaca Linn on Parameters Affecting Reproduction in Rats

OBJECTIVE

Aqueous extract of unripe Musa paradisiaca fruit is commonly used for the treatment of ulcers in eastern Nigeria. This study aimed to assess the acute and subacute effects of an aqueous extract of unripe fruit on male and female fertility in rats.

METHODS

Aqueous extracts obtained by maceration were analyzed for acute and subacute toxicity and for the presence of phytochemical constituents using standard procedures. The extract (100, 500, and 1000 mg/kg) was administered daily to rats of both sexes for 28 d. Blood samples collected on days 0 and 28 were assessed for follicle-stimulating hormone (FSH), luteinizing hormone (LH), catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA). Testes and ovaries were harvested for histopathological analysis. Sperm were also collected to determine the sperm count and motility.

RESULTS

Phytochemical screening revealed the presence of saponins, tannins, alkaloids, and resins. After an oral dose of up to 5000 mg/kg, there were no deaths in the acute toxicity test. The extract (500 mg/kg) significantly (P < .05) enhanced sperm count and motility relative to the untreated control; significantly (P < .05) reduced SOD, CAT, and glutathione levels, while significantly (P < .05) elevated LH, FSH, and MDA levels in male and female rats. Histological examination revealed significant structural damage to the ovaries.

CONCLUSION

Unripe Musa paradisiaca fruit exhibited an adverse toxicological profile following prolonged administration and caused oxidative stress in rodents.

Development of a biomolecular approach to identify sperm functions and fertility using sperm RNAs

Infertility affects a significant percentage of couples worldwide, and male factors contribute significantly to this problem. Traditional assessments of male fertility rely primarily on parameters such as sperm motility, morphology, viability, and concentration. However, these metrics often do not provide a comprehensive understanding of sperm function, which is critical not only for fertilization but also for successful embryo development. Herein, we used porcine spermatozoa as a model to investigate the potential of sperm RNA markers in assessing various aspects of sperm function from motility to fertility. Using artificial insemination, we evaluated male fertility based on the litter size of sows inseminated with sperm from 20 boars. In addition, we measured parameters such as weaning rate, death births, live births, and mummy births. Sperm functional parameters, including motility and kinematics, were assessed before and after in vitro capacitation. Finally, correlations between various sperm functional parameters and sperm RNA markers were explored. Our results revealed interesting relationships between sperm functional parameters. While motility and kinematics were correlated, they were not correlated with sperm capacitation status. Surprisingly, no significant correlations were found between these parameters and male fertility. However, specific parameters of sperm capacitation status after in vitro capacitation were correlated with weaning rate and live births, highlighting their importance in predicting successful fertilization. Further analysis of sperm RNA markers identified genes related to male fertility, including IZUMO1, known for its role in sperm-egg fusion. These genes showed correlations with motility, capacitation, and fertilization parameters, shedding light on their potential roles in sperm function. In conclusion, our study demonstrates that sperm RNA markers hold promise for the diagnosis and prognosis of various aspects of sperm function, providing valuable insights into male infertility. These markers may serve as diagnostic tools to improve our understanding of male fertility problems, ultimately benefiting couples struggling with infertility.

Sperm proteostasis: Can-nabinoids be chaperone's partners?

The male gamete is a highly differentiated cell that aims to fuse with the oocyte in fertilization. Sperm have silenced the transcription and translational processes, maintaining proteostasis to guarantee male reproductive health. Despite the information about the implication of molecular chaperones as orchestrators of protein folding or aggregation, and the handling of body homeostasis by the endocannabinoid system, there is still a lack of basic investigation and random controlled clinical trials that deliver more evidence on the involvement of cannabinoids in reproductive function. Besides, we noticed that the information regarding whether recreational marijuana affects male fertility is controversial and requires further investigation. In other cell models, it has recently been evidenced that chaperones and cannabinoids are intimately intertwined. Through a literature review, we aim to explore the interaction between chaperones and cannabinoid signaling in sperm development and function. To untangle how or whether this dialogue happens within the sperm proteostasis. We discuss the action of chaperones, the endocannabinoid system and phytocannabinoids in sperm proteostasis. Reports of some heat shock and lipid proteins interacting with cannabinoid receptors prove that chaperones and the endocannabinoid system are in an intimate dialogue. Meanwhile, advancing the evidence to decipher these mechanisms for introducing innovative interventions into routine clinical settings becomes crucial. We highlight the potential interaction between chaperones and cannabinoid signaling in regulating proteostasis in male reproductive health.

Chromatin condensation but not DNA integrity of pig sperm is greater in the sperm-rich fraction

BACKGROUND

Protamination and condensation of sperm chromatin as well as DNA integrity play an essential role during fertilization and embryo development. In some mammals, like pigs, ejaculates are emitted in three separate fractions: pre-sperm, sperm-rich (SRF) and post sperm-rich (PSRF). These fractions are known to vary in volume, sperm concentration and quality, as well as in the origin and composition of seminal plasma (SP), with differences being also observed within the SRF one. Yet, whether disparities in the DNA integrity and chromatin condensation and protamination of their sperm exist has not been interrogated.

RESULTS

This study determined chromatin protamination (Chromomycin A3 test, CMA3), condensation (Dibromobimane test, DBB), and DNA integrity (Comet assay) in the pig sperm contained in the first 10 mL of the SRF (SRF-P1), the remaining portion of the sperm-rich fraction (SRF-P2), and the post sperm-rich fraction (PSRF). While chromatin protamination was found to be similar between the different ejaculate fractions (P > 0.05), chromatin condensation was seen to be greater in SRF-P1 and SRF-P2 than in the PSRF (P = 0.018 and P = 0.004, respectively). Regarding DNA integrity, no differences between fractions were observed (P > 0.05). As the SRF-P1 has the highest sperm concentration and ejaculate fractions are known to differ in antioxidant composition, the oxidative stress index (OSi) in SP, calculated as total oxidant activity divided by total antioxidant capacity, was tested and confirmed to be higher in the SRF-P1 than in SRF-P2 and PSRF (0.42 ± 0.06 vs. 0.23 ± 0.09 and 0.08 ± 0.00, respectively; P < 0.01); this index, in addition, was observed to be correlated to the sperm concentration of each fraction (Rs = 0.973; P < 0.001).

CONCLUSION

While sperm DNA integrity was not found to differ between ejaculate fractions, SRF-P1 and SRF-P2 were observed to exhibit greater chromatin condensation than the PSRF. This could be related to the OSi of each fraction.

Ensembling noisy segmentation masks of blurred sperm images

BACKGROUND

Sperm tail morphology and motility have been demonstrated to be important factors in determining sperm quality for in vitro fertilization. However, many existing computer-aided sperm analysis systems leave the sperm tail out of the analysis, as detecting a few tail pixels is challenging. Moreover, some publicly available datasets for classifying morphological defects contain images limited only to the sperm head. This study focuses on the segmentation of full sperm, which consists of the head and tail parts, and appear alone and in groups.

METHODS

We re-purpose the Feature Pyramid Network to ensemble an input image with multiple masks from state-of-the-art segmentation algorithms using a scale-specific cross-attention module. We normalize homogeneous backgrounds for improved training. The low field depth of microscopes blurs the images, easily confusing human raters in discerning minuscule sperm from large backgrounds. We thus propose evaluation protocols for scoring segmentation models trained on imbalanced data and noisy ground truth.

RESULTS

The neural ensembling of noisy segmentation masks outperforms all single, state-of-the-art segmentation algorithms in full sperm segmentation. Human raters agree more on the head than tail masks. The algorithms also segment the head better than the tail.

CONCLUSIONS

The extensive evaluation of state-of-the-art segmentation algorithms shows that full sperm segmentation is challenging. We release the SegSperm dataset of images from Intracytoplasmic Sperm Injection procedures to spur further progress on full sperm segmentation with noisy and imbalanced ground truth. The dataset is publicly available at https://doi.org/10.34808/6wm7-1159.

Long-read-based single sperm genome sequencing for chromosome-wide haplotype phasing of both SNPs and SVs

Although localized haploid phasing can be achieved using long read genome sequencing without parental data, reliable chromosome-scale phasing remains a great challenge. Given that sperm is a natural haploid cell, single-sperm genome sequencing can provide a chromosome-wide phase signal. Due to the limitation of read length, current short-read-based single-sperm genome sequencing methods can only achieve SNP haplotyping and come with difficulties in detecting and haplotyping structural variations (SVs) in complex genomic regions. To overcome these limitations, we developed a long-read-based single-sperm genome sequencing method and a corresponding data analysis pipeline that can accurately identify crossover events and chromosomal level aneuploidies in single sperm and efficiently detect SVs within individual sperm cells. Importantly, without parental genome information, our method can accurately conduct de novo phasing of heterozygous SVs as well as SNPs from male individuals at the whole chromosome scale. The accuracy for phasing of SVs was as high as 98.59% using 100 single sperm cells, and the accuracy for phasing of SNPs was as high as 99.95%. Additionally, our method reliably enabled deduction of the repeat expansions of haplotype-resolved STRs/VNTRs in single sperm cells. Our method provides a new opportunity for studying haplotype-related genetics in mammals.

Canine Semen Evaluation and Processing

Advances in canine semen evaluation have progressed over time in fits and spurts, interspersed with long periods of relative inactivity. Despite exciting advances in the semen analysis, clinical canine theriogenology has been in a period of relative inactivity for a number of decades since initial advances in canine semen freezing in the mid 20th century. This review describes ways that the clinical practice of canine semen evaluation should improve, given the state of current knowledge.

Loss of mammalian glutaminase orthologs impairs sperm function in Caenorhabditis elegans

The decline in sperm function is a major cause of human male infertility. Glutaminase, a mitochondrial enzyme that catalyzes the hydrolysis of glutamine to generate glutamate, takes part in many diverse biological processes such as neurotransmission, metabolism, and cellular senescence. Here we report the role of glutaminase in regulating sperm function. By generating a triple mutant that harbors a loss-of-function allele for each of all three mammalian glutaminase orthologs, we found that glutaminase gene activity is required for optimal Caenorhabditis elegans sperm function. Tissue-specific gene manipulations showed that germline glutaminase activity plays an important role. Moreover, transcriptional profiling and antioxidant treatment suggested that glutaminase promotes sperm function by maintaining cellular redox homeostasis. As maintaining a low level of ROS is crucial to human sperm function, it is very likely that glutaminase plays a similar role in humans and therefore can be a potential target for treating human male infertility.

Subclinical Hypothyroidism and Sperm DNA Fragmentation: A Cross-sectional Study of 5401 Men Seeking Infertility Care

CONTEXT

Our previous study showed that paternal subclinical hypothyroidism (SCH) had a detrimental effect on the clinical outcomes of assisted reproductive technologies. However, it remains to be determined whether paternal SCH affects sperm DNA integrity.

OBJECTIVE

To investigate the association between SCH and sperm DNA fragmentation in men seeking infertility care.

METHODS

This cross-sectional study included 4983 men with euthyroidism and 418 men with SCH seeking infertility treatment in a tertiary care academic medical center between January 2017 and December 2021. The outcome measures were the absolute DNA fragmentation index (DFI) and the risk of abnormal DFI (defined as DFI ≥ 25% or ≥ 30%).

RESULTS

The mean (SD) age of men with euthyroidism and men with SCH was 34.20 (5.97) and 35.35 (6.48) years, respectively (P < 0.001). The difference in DFI was not statistically significant (adjusted mean: 19.7% vs 18.9% in the SCH and euthyroidism groups, respectively; P = 0.07) after confounder adjustment. A DFI ≥25% was significantly more frequent in men with SCH (20.57%) than in men with euthyroidism (14.49%) after confounder adjustment [odds ratio (OR) 1.43 (95% CI 1.09-1.88)]. DFI ≥ 30% was also significantly more common in men with SCH (11.72%) than in men with euthyroidism [6.74%; OR 1.84 (95% CI 1.34-2.52)]. In addition, thyroid-stimulating hormone concentration was significantly associated with an increased risk of having a DFI ≥25% (P < 0.001) or ≥30% (P = 0.011).

CONCLUSION

SCH was significantly associated with an increased risk of an abnormal DFI.

Multiomics analysis of male infertility

Infertility affects 8-12% of couples globally, and the male factor is a primary cause in approximately 50% of couples. Male infertility is a multifactorial reproductive disorder, which can be caused by paracrine and autocrine factors, hormones, genes, and epigenetic changes. Recent studies in rodents and most notably in humans using multiomics approach have yielded important insights into understanding the biology of spermatogenesis. Nonetheless, the etiology and pathogenesis of male infertility are still largely unknown. In this review, we summarized and critically evaluated findings based on the use of advanced technologies to compare normal and obstructive azoospermia (OA) versus non-obstructive azoospermia (NOA) men, including whole-genome bisulfite sequencing (WGBS), single cell RNA-seq (scRNA-seq), whole exome sequencing (WES), and ATAC-seq. It is obvious that the multiomics approach is the method of choice for basic research and clinical studies including clinical diagnosis of male infertility.

Evolution of the World Health Organization semen analysis manual: where are we?

The WHO (World Health Organization) manuals provide state-of-the-art guidance on how a semen analysis should be carried out. The much anticipated sixth edition of the WHO semen analysis manual has been released 10 years after its previous version and includes essential updates, such as new reference standards for semen volume and microscopic sperm characteristics of recent fathers. A well-conducted semen analysis remains an essential foundation of the infertility evaluation process and affects patient referral, diagnosis and treatment. However, a male infertility work-up primarily based on routine semen analysis does not provide men with an optimal fertility pathway; the primary reasons for routine semen analysis inadequacy in this context include its low predictive value for natural and assisted conception success, its inability to detect sperm DNA and epigenetic deficiencies that might negatively affect embryo development, implantation and offspring well-being, and the substantial overlap between semen parameters of fertile and subfertile individuals. Ideally, a full andrological assessment should be carried out by reproductive urologists in all men dealing with couple infertility and should include a detailed history analysis, physical examination, semen analysis, endocrine assessment and other tests as needed. Only through a complete male infertility work-up will relevant underlying medical and infertility conditions be revealed and potentially treated or alleviated. The ultimate goals of a comprehensive andrological assessment are to positively influence overall male health, pregnancy prospects and offspring well-being.

Lab on a chip devices for fertility: from proof-of-concept to clinical impact

Microfluidics offers tremendous opportunities to understand the underlying biology of fertilization at the single-cell level and improve infertility management, however, its true clinical impact is yet to be realized. Lab-on-a-chip devices have generally failed to diffuse into clinical practice due to issues associated with their translation or their practicality and performance in clinical settings. In this perspective, I reflect on how the full potential of microfluidic technologies for fertility can be realized by considering regulatory and manufacturing considerations at the development stage and by redefining our developmental goals to directly target the ultimate clinical needs. I also challenge the common rationale around developing technologies for infertility treatment based on reducing cost and complexity in operation as the ultimate outcome is invaluable, human life.

Cell-Cell Interaction-Mediated Signaling in the Testis Induces Reproductive Dysfunction—Lesson from the Toxicant/Pharmaceutical Models

Emerging evidence has shown that cell-cell interactions between testicular cells, in particular at the Sertoli cell-cell and Sertoli-germ cell interface, are crucial to support spermatogenesis. The unique ultrastructures that support cell-cell interactions in the testis are the basal ES (ectoplasmic specialization) and the apical ES. The basal ES is found between adjacent Sertoli cells near the basement membrane that also constitute the blood-testis barrier (BTB). The apical ES is restrictively expressed at the Sertoli-spermatid contact site in the apical (adluminal) compartment of the seminiferous epithelium. These ultrastructures are present in both rodent and human testes, but the majority of studies found in the literature were done in rodent testes. As such, our discussion herein, unless otherwise specified, is focused on studies in testes of adult rats. Studies have shown that the testicular cell-cell interactions crucial to support spermatogenesis are mediated through distinctive signaling proteins and pathways, most notably involving FAK, Akt1/2 and Cdc42 GTPase. Thus, manipulation of some of these signaling proteins, such as FAK, through the use of phosphomimetic mutants for overexpression in Sertoli cell epithelium in vitro or in the testis in vivo, making FAK either constitutively active or inactive, we can modify the outcome of spermatogenesis. For instance, using the toxicant-induced Sertoli cell or testis injury in rats as study models, we can either block or rescue toxicant-induced infertility through overexpression of p-FAK-Y397 or p-FAK-Y407 (and their mutants), including the use of specific activator(s) of the involved signaling proteins against pAkt1/2. These findings thus illustrate that a potential therapeutic approach can be developed to manage toxicant-induced male reproductive dysfunction. In this review, we critically evaluate these recent findings, highlighting the direction for future investigations by bringing the laboratory-based research through a translation path to clinical investigations.

Strategies and Perspectives for UV Resonance Raman Applicability in Clinical Analyses of Human Sperm RNA

Developing a deeper knowledge about the impact of DNA and RNA epigenetic mutations on sperm production and fertilization performance is essential for selecting best quality samples in Assisted Reproductive Technologies (ART). Indeed, sperm RNAs adenine and guanine are likely to be methylated in low quality RNA sperm samples and their study requires the employment of techniques able to isolate high quality nucleic acids. UV resonance Raman spectroscopy represents a valuable tool that is able to monitor peculiar molecular modifications occurring predominantly in nucleic acids, being less sensitive to the presence of other biological compounds. In this work, we used an UV Resonance Raman (UVRR) setup coupled to a synchrotron radiation source tuned at 250 nm, in order to enhance sperm RNAs adenine and guanine vibrational signals, reducing also the impact of a fluorescence background typically occurring at lower energies. Despite that our protocol should be further optimized and further analyses are requested, our results support the concept that UVRR can be applied for setting inexpensive tools to be employed for semen quality assessment in ART.